lagg(4) and failover

[Peter Jeremy]

On 2008-Aug-12 18:55:52 +0800, Eugene Grosbein <eugen at kuzbass.ru> wrote:
>On Tue, Aug 12, 2008 at 12:37:15PM +0200, Marian Hettwer wrote:
>
>> I'm using lagg(4) on some of our servers and I'm just wondering how the
>> failover is implemented.

As far as I can tell, not especially well :-(.  It doesn't seem to detect
much short of layer 1 failure.  In particular, shutting down the switch
port will not trigger a failover.

>> The manpage isn't quite clear:
>> 
>>      failover     Sends and receives traffic only through the master port. 
>> If
>>                   the master port becomes unavailable, the next active port
>> is
>>                   used.  The first interface added is the master port; any
>>                   interfaces added after that are used as failover devices.
>> 
>> What is meant by "becomes unavailable"? Is it just the physical link which
>> needs to become unavailable to trigger a failover?

It seems to be,

>Yes. It seems you need lacp protocol described later in the manual.

Actually, lacp and failover are used differently: lacp is primarily
used to increase the bandwidth between the host and the switch whilst
failover is used for redundancy.

With lacp, all the physical interfaces must be connected to a single
switch.  With failover, the physical interfaces will normally be
connected to different switches (so a failure in one switch will not
cause the loss of all connectivity.

-- 
Peter Jeremy
Please excuse any delays as the result of my ISP's inability to implement
an MTA that is either RFC2821-compliant or matches their claimed behaviour.
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